Unknown,Transcriptomics,Genomics,Proteomics

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Gene expression responses to chronic low dose arsenite exposure

ABSTRACT: Arsenic (As) exposure is a significant worldwide environmental health concern. Low dose, chronic arsenic exposure has been associated with higher risk of skin, lung, and bladder cancer, as well as cardiovascular disease and diabetes. While arsenic-induced biological changes play a role in disease pathology, little is known about the dynamic cellular changes due to arsenic exposure and withdrawal. In these studies, we seek to understand the molecular mechanisms behind the biological changes induced by chronic low doses of arsenic exposure. We used a comprehensive approach involving chromatin structural studies and mRNA microarray analyses to determine how chromatin structure and gene expression patterns change in response to chronic low dose arsenic exposure and its subsequent withdrawal. Our results show that cells exposed to low doses of sodium arsenite have distinct temporal and coordinated chromatin, gene expression and miRNA changes that are consistent with differentiation and activation of multiple biochemical pathways. Most of these temporal patterns in gene expression are reversed when arsenic was withdrawn. However, some of the gene expression patterns remained altered, plausibly as a result of an adaptive response by these cells. Additionally, these gene expression patterns correlated with changes in chromatin structure, further solidifying the role of chromatin structure in gene regulatory changes due to arsenite exposure. Lastly, we show that arsenite exposure influences gene regulation both at the transcription initiation as well as at the splicing level. Thus our results suggest that general patterns of alternative splicing, as well as expression of particular gene regulators, can be indicative of arsenite-induced cell transformation. A total of eight (8) samples with two biological replicates under four separate conditions: wild-type treated with deionized H2O for 36 days (NT); chronic low-dose arsenic exposure of 1 uM of sodium arsenite (iAs-T) for 36 days; chronic arsenic exposure of 1 uM of sodium arsenite for 26 days followed by removal of sodium arsenite for 10 days, measured at day 36 (iAs-Rev); and chronic arsenic exposure of 1 uM of sodium arsenite for 26 days, followed by removal of sodium arsenite exposure for 10 days, followed by 1 uM of chronic sodium arsenite exposure for 10 days (measured at day 46) (iAs-Rev-T).

ORGANISM(S): Homo sapiens

SUBMITTER: Eric Rouchka

PROVIDER: E-GEOD-60760 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Inorganic Arsenic-induced cellular transformation is coupled with genome wide changes in chromatin structure, transcriptome and splicing patterns.

Riedmann Caitlyn C Ma Ye Y Melikishvili Manana M Godfrey Steven Grason SG Zhang Zhou Z Chen Kuey Chu KC Rouchka Eric C EC Fondufe-Mittendorf Yvonne N YN

BMC genomics 20150319

<h4>Background</h4>Arsenic (As) exposure is a significant worldwide environmental health concern. Low dose, chronic arsenic exposure has been associated with a higher than normal risk of skin, lung, and bladder cancer, as well as cardiovascular disease and diabetes. While arsenic-induced biological changes play a role in disease pathology, little is known about the dynamic cellular changes resulting from arsenic exposure and withdrawal.<h4>Results</h4>In these studies, we sought to understand th ...[more]

PMID: 25879800

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Project description:Inorganic arsenic, a major environmental contaminant, has risen as an important health problem worldwide. More detailed identification of the molecular mechanisms associated with iAs exposure would help to establish better strategies for prevention and treatment. Although chronic iAs exposures have been previously studied there is little to no information regarding the early events of exposure to iAs. To better characterize the early mechanisms of iAs exposure we conducted gene expression studies using sublethal doses of iAs at two different time-points. The major transcripts differentially regulated at 2 hrs of iAs exposure included antioxidants, detoxificants and chaperones. Moreover, after 12 hrs of exposure many of the down-regulated genes were associated with DNA replication and S phase cell cycle progression. Interestingly, the most affected biological pathway by both 2 or 12 hrs of iAs exposure were the Nrf2-Keap1 pathway, represented by the highly up-regulated HMOX1 transcript, which is transcriptionally regulated by the transcription factor Nrf2. Additional Nrf2 targets included SQSTM1 and ABCB6, which were not previously associated with acute iAs exposure. Signalling pathways such as interferon, B cell receptor and AhR route were also responsive to acute iAs exposure. Since HMOX1 expression increased early (20 min) and was responsive to low iAs concentrations (0.1 M-oM-^AM--M), this gene could be a suitable early biomarker for iAs exposure. In addition, the novel Nrf2 targets SQSTM1 and ABCB6 could play an important and previously unrecognized role in cellular protection against iAs We used human lymphoblastoid cell line (CL-1), immortalized with Epstein-Barr virus. Cell cultures were propagated in RPMI media supplemented with 10% fetal bovine serum (FBS), L-glutammine 2 mM and antiobiotics penicillin and 10 mg/ml streptomycin) at 37M-BM-:C in an atmosphere of 5% CO2. In the case of primary cultures, 1% phytohemaglutinine were added. Cell cultures (1x106) were treated with 5M-BM-5M sodium arsenite for 2 and 12 hrs while control cultures were incubated with PBS. Nine biological replicates for each condition were used for microarray analysis. After iAs treatment, total RNA from each biological replicate was isolated with Trizol. From the 9 biological replicates performed on each condition, we generated 3 pools at a concentration of 300 ng/M-BM-5L, where each pool was processed to a single microarray platform.

Project description:Folate deficiency, arsenic exposure, and gamma-IR are known developmental toxicants and have carcinogenic effects. The mechanism by which IR is known, but the effect of arsenic or folate deficiency remains unclear. Their effect may be mediated by epigenetic alterations, leading to miRNA expression changes, and this experiment examined this hypothesis We used microarrays to detail the miRNA expression profiles of TK6 cells treated with 2 uM sodium arsenite for 6 days, folate-deficient media for 6 days, or 2.5 Gy IR exposure either acutely at 4 hours post exposure or long-term at 6 days post exposure, as well as requiste controls, all in biological triplicate. Keywords: exposure differences TK6, were cultured in standard RPMI 1640 (Invitrogen Inc., Gaithersburg, MD) or folate-deficient RPMI 1640 (Invitrogen). Growth media was supplemented with 10% fetal bovine serum (Invitrogen) and 1% penicillin-streptomycin; dialyzed fetal bovine serum (Invitrogen) was added to the folate-deficient medium in order to eliminate folic acid in the serum. For controls, folate-deficiency, arsenic exposure, and 6-day ?-IR exposure groups, 106 cells were diluted into 50ml of appropriate growth media. For the 4-hour post-?-IR exposure group, 107 cells were diluted into 50ml of growth media. For the arsenic exposed group, sodium arsenite was added to the media to a concentration of 2 ?M. For the ?-IR exposure groups, cells were diluted and allowed to incubate for 4 hours prior to irradiation treatment, and were exposed at a dose rate of 86.76 rad/min to a final dose of 2.5 Gy using a Philips MGC-40 X-ray source. Following exposure, cells were returned to the incubator. After fours hours, the short-term post-??-IR exposure group was collected for RNA isolation, as well as a mock (control) group. All experimental and control conditions were performed in triplicate. For all other groups, cells were cultured for 6 days, with the media changed and renewed, with the appropriate treatment, on day 3.

Dataset Information

Gene expression responses to chronic low dose arsenite exposure

Publications

Inorganic Arsenic-induced cellular transformation is coupled with genome wide changes in chromatin structure, transcriptome and splicing patterns.

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